1. Field of the Invention
The present invention relates to the manufacture of nonwoven fabrics. More specifically, it relates to endless fabric belts on which nonwoven fabrics are formed and/or conveyed during their manufacture.
2. Description of the Prior Art
The production of nonwoven fabrics is well known in the art. Such fabrics are produced directly from fibers without conventional spinning, weaving or knitting operations. Instead, they may be produced by spin-bonding or melt-blowing processes in which newly extruded fibers are laid down to form a web while still in a hot, tacky condition following extrusion, whereby they adhere to one another to yield an integral web.
Nonwoven fabrics may also be produced by air-laying or carding operations where the web of fibers is consolidated, subsequent to deposition, into a nonwoven fabric by needling or hydroentanglement. In the latter, high-pressure water jets are directed vertically down onto the web to entangle the fibers with each other. In needling, the entanglement is achieved mechanically through the use of a reciprocating bed of barbed needles which force fibers on the surface of the web further thereinto during the entry stroke of the needles.
Endless fabric belts play a key role in these processes. Generally, these take the form of fine-mesh screens woven from plastic monofilament, although metal wire may be used instead of plastic monofilament when temperature conditions during a nonwovens manufacturing process make it impractical or impossible to use plastic monofilament.
Typically, the plastic monofilaments and metal wires have smooth surfaces. As a consequence, the surfaces of the endless fabric belts used in the nonwovens manufacturing process are also smooth. While such surfaces are highly desirable for most paper machine clothing, in nonwovens manufacture such a surface can render forming and conveying operations unstable because slippage or movement by the nonwoven fabric being manufactured, relative to the endless fabric belt, in either the machine direction, the cross-machine direction, or in both of these directions, can occur.
The present invention provides a solution to this problem in the form of an endless fabric belt having a degree of surface roughness or texture to inhibit movement or slippage of a nonwoven fabric relative thereto.
Accordingly, the present invention is an improvement for an industrial fabric of the variety used in the form of an endless fabric belt to form and convey a nonwoven fiber web during the manufacture of a nonwoven fabric therefrom. The industrial fabric is woven from warp and weft yarns, and has a web-supporting surface.
The improvement is that at least some of one of the warp and weft yarns on the web-supporting surface of the industrial fabric are rough-surface yarns, which inhibit the movement of a nonwoven fiber web being conveyed on the web-supporting surface from moving relative thereto. The rough-surface yarns may be in one or both directions on the web-supporting surface of the industrial fabric, and may be some or all of the yarns in that direction or in both directions. Preferably, at least some of the rough-surface yarns make long floats on the web-supporting surface of the industrial belt.
The rough-surface yarns may be striated monofilaments or multistrand yarns, the latter being a plurality of filaments either twisted about one another or braided together. The rough surfaces of these yarns, as opposed to the smooth surfaces of the monofilament yarns customarily used in industrial fabrics of the present variety, provide the industrial fabrics with a unique surface roughness or texture which enables them to convey a nonwoven fiber web without slippage, while having minimal impact on such desirable characteristics as air permeability and web release.
The present invention will now be described in more complete detail with frequent reference being made to the drawings identified below.